Gear pump 1371504 223441458 2008-07-04T02:33:04Z Javawizard 2442687 /* Applications */ Changed lbf/in2 to psi [[Image:Gear pump exploded.png|thumb|right|320px|An exploded view of an external gear pump.]] [[Image:Internal_gear_pump.gif‎|thumb|right|320px|Water flows from left to right in this [[Gerotor]] pump]] A '''Gear pump''' uses the meshing of gears to pump fluid by displacement. They are one of the most common types of [[pump]]s for [[hydraulic machinery|hydraulic fluid power]] applications. Gear pumps however are also widely used in chemical installations to pump fluid with a certain viscosity. There are two main variations; ''external gear pumps'' which use two external [[gear|spur gear]]s, and ''internal gear pumps'' which use an external and an internal spur gear. Gear pumps are ''fixed displacement'', meaning they pump a constant amount of fluid for each revolution. Some gear pumps are designed to function as either a [[motor]] or pump. ==Theory of operation== As the gears rotate they separate on the intake side of the pump, creating a void and suction which is filled by [[fluid]]. The fluid is carried by the gears to the discharge side of the pump, where the meshing of the gears displace the fluid. The mechanical clearances are small&mdash;on the order of a thousandth of an inch (micrometres). The tight clearances, along with the speed of rotation, effectively prevent the fluid from leaking backwards. The rigid design of the gears and housing allow for very high pressures and the ability to pump highly [[viscosity|viscous]] fluids. Many variations exist, including; helical and herringbone gear sets (instead of spur gears), lobe shaped rotors similar to Roots Blowers (commonly used as [[superchargers]]), and mechanical designs that allow the stacking of pumps. The most common variations are shown below (the drive gear is shown <font color=blue>blue</font> and the idler is shown <font color=purple>purple</font>). <Gallery> Image:Gear pump.png| External gear pump design for [[hydraulic machinery|hydraulic power]] applications. Image:Gear pump 2.png| Internal gear ([[Gerotor]]) pump design for [[internal combustion engine|automotive]] oil pumps. Image:Gear pump 3.png| Internal gear (Gerotor) pump design for high [[viscosity]] fluids. </Gallery> Suction and pressure ports need to interface where the gears mesh (shown as dim gray lines in the internal pump images). Some internal gear pumps have an additional, crescent shaped seal (shown above, right). Pump formulas: *Flow rate in US gal/min = Displacement X rpm/231 (displacement in in<sup>3</sup>/revolution) *Power in hp = US gal/min X (lbf/in³)/1714 ==Applications== ''External gear pumps'' are the most common type of pump for hydraulic power applications. This is because of their simplicity, reliability, and very high power ratings. A typical 10 hp (7 kW) gear pump may fit into a 4 x 4 x 4 inch (100 by 100 by 100 mm) envelope, a fraction of the size of a comparable electric motor. Maximum operating pressures are between 1000 and 4000 [[Pounds per square inch|psi]] (7 and 28 MPa, 70 - 280 bar). Many commercial models are designed to operate as either a motor or pump. Some designs add [[Load sensing (hydraulics)|load sensing]] modifications. ''Internal gear pumps'' perform better at lower speeds and with higher viscosity fluids than external gear pumps. [[internal combustion engine|Engine]] [[oil pump]]s are usually internal gear designs. Industry standards exist for gear pump mounting flanges, drive shaft sizes and splines, and ports. The suction port will usually be larger than the pressure port to reduce the possibility of [[cavitation]]. ==See also== *[[Gerotor]] *[[Hydraulic pump]] *[[Vane pump]] ==External links== {{Commons|Gear pump}} *[http://www.pumpschool.com/principles/external.htm External gear pump description] *[http://www.pumpschool.com/principles/internal.htm Internal gear pump description] *[http://www.hydraulic-equipment-manufacturers.com/hydraulic-articles1.html Gear pump article] [[Category:Pumps]] [[bs:Zupčasta pumpa]] [[cs:Zubové čerpadlo]] [[de:Zahnradpumpe]] [[et:Hammasrataspump]] [[hr:Zupčasta sisaljka]] [[nl:Tandwielpomp]] [[ja:歯車ポンプ]]